This invention relates to a check valve for a fluid delivery system for delivering a plurality of fluids, in sequence to a treatment reservoir.
Prior to the present invention, fluid delivery systems have been available which minimize system volume and which minimize intermixing of fluids while delivering a precise amount of a fluid for chemical reaction. These systems are generally utilized for chemical processes involving a large number of sequentially effected chemical reactions such as in protein synthesis, deoxyribo- nucleic acid (DNA) synthesis or when sequencing proteins.
U.S. Pat. No. 4,008,736 discloses a valve block containing a capillary formed of capillary segments bored at about 30.degree. from a contact surface of the block. The junctions of the capillary segments are effected at the contact surface and within the block. The junctions at the contact surfaces form valving sites to which are engaged apertured sliding blocks which effect fluid communication with the capillary. While the sliding blocks are effective in providing the desired fluid flow, they wear rapidly thereby causing undesirable leaks.
U.S. Pat. No. 4,168,724 discloses a similar device but replaces the slider valves with diaphragm check valves. The fluid is delivered through the check valves from a pressurized fluid storage source. This system requires a vacuum assist to open the valves. This system is undesirable because the type of diaphragm valve used is undesirably susceptible to particulate contamination. In addition, the pressure drop through the valves is difficult to control which causes inaccurate reagent delivery.
U.S. Pat. No. 4,558,845 discloses a fluid delivery system utilizing a valve block assembly comprising a separate block for each valve site. The common conduit to the reaction site is alternately a channel in a block and tubing connecting two adjacent blocks. This arrangement requires a plurality of fittings which are subject to leaking.
U.S. Pat. No. 4,773,446 discloses a valve block assembly which utilizes diaphragm check valves. The check valves serve to control fluid flow from a plurality of pressurized fluid reservoirs, in sequence to a common outlet reservoir. This system requires the use of conduits from the fluid reservoirs and fittings to valve blocks for each conduit. These fittings are subject to leakage.
The fluid delivery system of the prior art depend upon the use of positive pressure to deliver the fluid and upon the control of block pressure to the fluid reservoir in order to precisely control the amount of fluid delivered to a treatment reservoir. These systems require the frequent adjustment of the fluid delivery means as a function of back pressure. All of the systems set forth above depend upon precise control of reservoir pressure and restriction through the valves to control reagent delivery volume. They are very sensitive to variations of the removable reaction column as regards the delivery volume and flow rate. Also these systems deliver fluids against back pressures only up to about 10 psig. It would be desirable to provide a system which eliminates the need of adjustment of the fluid delivery means. It would also be desirable to provide a means to deliver fluids which is independent of back pressure. Such a system would permit delivery of accurate volumes of reagents which would result in improved system performance and reduced reagent consumption.
It would also be desirable to provide a fluid delivery system which minimizes the use of tubes and tube fittings while minimizing the volume of the system as compared to presently available systems.